Wave transmission system



June 12, 1928.

J. F. FARRINGTON w1 wE TRANSMISSION SYSTEM hue/flow.- John E f'drr'myfm Patented June 12, 1928.

UNITED S ATES PATENT OFFICE.

JOHN FISH mname'ron, or FL sHm N awjYonk, AssIenoB To wiisrnnn TRIC COMPANY, INCORPORATED, or mw YORK, N. -Y., A conrone'rronor NEW YORK.

" W VE TRANS IS ION SYSTEM.

Application filed September 28, 192 sent-um. 503,906. Renewed June a, 1927.

This invention relates to improvements intwo-way radio telephone systems similar signaling systems. I

A type of system hitherto invented by the present applicant is one in which a certain portion of the energy of theoutgomgcarrier frequency wave is combined with thereceived signals to produce an auxihary carrier wave. lVhen signals are being transmitted, the auxiliaryv carrier wave'is modulated in accordance with the transmitted signals; when. signalsare being received, the auxiliary carrier wave is n'iodulatedin accordance with the receivedsignals; and when transmission and reception of signals occur simultaneously, theauxiliary carrier wave is modulated inaccorda'nce with both'the received and transmittedsignals. A particular instance of the application of such a system is in a radio telephone system for a twowav conversation wherein transmission and reception ordinarily take place alternately and not simultaneously. lucase'however, one party desires to interrupt or break in upon the conservation of the other, th1s;1s

and other accoinplished Without the manipulation of any switch or the performance of any act other than merely talking into his telephone transmitter as is the case on an ordinary telephone line. 1 y

Objects ofthe invention are to improve the selectivity of the almv enientioned and other typesof system,to provide for the connection ofsuchsystems to ordinary telephone lines whereby conversations can take place partly by radio and partly over-line wires, to

other novel improved features as providearrangements whereby the amonnt of energy from the local transmitter 11npressed on the receiving clrcult Will not be sufficient-to impair the efficiency ofthe receiving circuit,eto provide for any desired degree of discrimination against the energy from the local transmitter in favor of energy from the distant transmitter, to provide channels for thetransmission and reception of telegraph or callin signals on the same carrier wave or waves on which telephone transmission is accomplished, and to provide hereinafter describ-edand claimed. i

l\-i[eans for attaining one or more of the above objects maybe embodied in various systems. In the preferred form, as describedherein, the transmitting antenna 18 used. Y

connected to anysuitable kind of radio telephone transmitter and the receiving antenna is connected to a suitable selective circuit to select the received waves andcombine them with energy of the transmitted Wave frequency. The receiving antenna is preferably designed to discriminate to a desiredextent against waves of thetransmitted frequency. The combined waves produce a combination frequency which is selectively transmitted and amplified and combined \vithjwaves of a third frequency to produce a second combination frequency which is'selectively transmitted and amplified andthereafter detected to produce the desired signal. The output circuit of the detector which performs the final detection is connected to a telephone line, to which is also connected, in conjugate relation, the input circuit of the radio telephone transmitter. A calling or telegra iihing channel is superimposed upon the talking channel in a manner hereinafter descr bed. a

For amore detaileddescription of the inventiomreference is made to theaccompany mg drawings, whereln Fig. 1 1s a circuit dia gram of a complete system embodying the invention, and Figs. 2 and 3 illustrate modified forms of antenna circuit which may be The circuit Tconstitutes a radio transmitter of auysuitable type. As herein 11- lustrated, high frequency oscillations from a source 1 of 800,000 cycles per second are impressed upon a 'thermionic amplifier tube 2 tothe output circuit of which is connected an-iinput circuit of a higher power thermionic amplifier 3. The output circuit of the aniplifier 23 is connected to the antenna 4 which typifies any suitable radiating circuit. A variable impedance system V is controlled by speech or other signaling waves transmitted over the telephone line TL. A circuit 5 connects the telephone'lin'e with the input circuit of the system V. Aspace current source Gsupplies the amplifiers2 and 3 and the system V through the iron core chokecoil 7 which is designcd'to have a high inductive reactance for variations of speech frequencies. Radio frequency choke coils Sserve to offer a high impedance to radio frequency currents, but a relatively low impedance to speech frequency"currents. Whenthe generator 1 is operat ng and sig- 45 frequencies.

55 the switch13 is closed.

naling waves are being received fromthe circuit 5,. there will beiprodueedin theiantenna 4 and radiated therefrom, signal modulated radio frequency waves. Thus, if the he 5 quency tit/the generator 1 incycles per second' be designated -f.;therewill -be radiated in addition to the frequency f side frequencies f is where 3 designates the signaling frequency. This is indicated by the legend f f is placed adjacent the antenna 4. Similar legends will be used throughout this specification to designate modulated carrier waves. y

The receiving antenna 9 ispleferably tuned II. by means of'a tuning capacityC orother suitable devicesto the mean frequencyofthe high frequency signaling waves which are to'be received. A tunedloop resonant circuit -10tuned'approximately orexaetly to W the frequency if may be placed in the antenna ,9 for causingthe antennacirouit to discriminate againstoscillations of the frequency f The circuit 10 maybe adjusted by changing 'its tnning or resistance'to give any desired degree of diccrimination equal to orzless than. the maxirnum which innght be secured by. proper adjustment. Coupled to theantenna .9 is a-circuit ll which is likewise preferably tuned to the mean of the received frequencies. i

It will first-be assumed that acarrier wave modulated by :a single signaling wave and represented by f f ia isto be received froma certain station with which communi- 85 cation isto be had. The communicating station maybe assumed to be transmitting on :a carrier 'wave of 1,030,000 cycles, that is, f,=1',030,000.- This 1,030,000 cycle pwave with its side frequencies will be superimposed upon the 800,000 cycle wave from the onic or other amplifier having one 101' more stages. A generator 12 is also coupled-to the input circuit of the deteQtorD -and supplies thereto a current having a frequency of 200,000 cycles. Let it be supposed'that In the output circuit of the detector D will be produced a current having a carrier frequency component of 30,000 cycles with side bands resulting from modulation. These currents will be selected 00 lav-the hand. filter or tuned circuits BF, am-

plified by the amplifier A end impressed npon the input circuit of the detector D The positions-'ofband-filter BF. and amplifier A may be interchanged. To the out- 05 put circuit of detector D; is connected :1

suitable .t I amplifier T FA speech frequenc band filter adapted to passe range 0 frequencies oftfmm 200 to 2,000 cycles as indicated on the drawing. The filter SF therefore transmits freely 'those frequencies which arefimost essential for the -reprotluction I (if-speech to the input circuit of the low frequency amplifier LFA whichmay'he of the thermionic or any other The. output circuit of the is connected to one of the windings of Ta- .threecoil transformer 14, ordinarily known as .a hybrid coil. 'The transformer 14 has one ,pair of terminals connected to the telephonetransmi ssion line TL and another pair of terminals connected to a balancing net FBN comprising electrical impedance elementsadapted to simulate the impedance of the .line TL at speech frequeneies. As will be ndted the circuit 15 is connected to the coil 14conjugately with respect torthe output circuit of the'amplifier LFA sothat if the balance is .perfect current variations inthe outputcircuit of the amplifier LFA will produce nopotential difference .across the terminals of the circuit 5. However, a large d e .of unbalance will not interfere with cient operation, explained hereinafter.

A .telegraphing or signaling channel is superimposed upon the speech frequency channel. By means of'this,thevarious carrier waves may be modulated in accordance with some frequencyeither above or below the speech range so as not to interfere with speech. Inithepresent instance, a frequency of 150 cycles is used. A 150- cycle generator 15 is included .in circuit with a key 16.

Whenthe key 16 is closed,1the. generator 15 will transmit an alternating current of 150 cycles through the speech frequency choke coils 17 to the-input circuit/of the variable impedance system V. Outgoing waves'from the transmitter T i will thereupon .be modulated in accordance with the 150 cycle wave.

A filter SF-is included in the-circuit 5to prevent the passage of speechfrequency components below 200 cycles. "This filter may pass arangeiof from 200 to 2,000 cycles or allfrequenciesabove 200 cycles. Thisprevents low frequency speech components-from acting on the relay 18.

Let it be assumed theta distant 'commnnieating station is sending out a wave of 1,030,000 cycles modulated in accordance with alow frequency wave of 150 cycles.

Then in the output circuit ofthe detector D tl1ere will be a component-of thislow frequency. Since this component cannot be transmitted through the speech frequency band filter SF, it will tmverse the low v.pass filter LPF which is designed to. passe range of frequencies of from 0 to 200- cycles. The receiving relay 18 will thereupon be-actuated. Thereceiving relay 18 may constitute a telegraph'sounder or other receiving instrument, or it may serve to close a circuit through a bell 19 or other equivalent calling having. a carrieryfrequency of 1,030,000

cycles are to be received. In this case it would be proper to design or adjust the band filter BF to pass a range of frequencies of from 228,000 to 232,000. cycles. Greater selectivity would thus be obtained. However, for the purpose about tobe described, the band filter BF is in the present instance designed or adjusted to pass a range offrequencies of from 208,000 to 232,000 cycles. Let it be supposed that in addition to modulated waves of the carrier frequency f it is desired to receive modulated waves of other carrier frequency f and i Let f be 1,020,000 cycles and f be 1,010,000 cycles.

Then in the output circuit of the detector D will be produced modulated waves having carrier frequencies of 210,000 and 220,000 cycles in addition to those previously mentioned having a frequency of 280,000 cycles. WVhen these various waves are combined with the waves from source 12, there will result in the output circuit of the detector D modulated waves of10,000, 20,000

and 30,000 cycles, each modulated in accordance with 1ts respective signal. Let it be assumedthat the switch13 is now opened,

which must be the case. in order to receive the several waves described. This places in circuit the channels C and C in addition to the channel G,,. Then the band filter BF in channel C, will select the 10,000 cycle modulated wave, band filter BF in channel C will select the 20,000 cycle modulated wave, and band filter BF in channel (1,, will select the 30,000 cycle modulated wave. The 30,000 cycle modulated wave will as before be detected to reproducethesignal or signals carried thereby in the manner hereinbefore described. This signal may be heard by a monitoring receiving telephone 20 connected across the output circuit of the band filter SF, if desired. Likewise, an operators transmitter 20 may be connected across the circuit 5, as illustrated. Components selected by the band filters, BF and BF respectively may be detected and heard'in receiving telephones 20 or impressedupon signaling lines. such as the line TL if desired. It will be understood, however, that whenever the transmitter T is operating, the. waves selected by the band filters BF, and BF,

will be modulated in, accordance with any signal which is at that instant IHIPIOSSGCl uponthe lnput circuit ofthe transmitter T.

Thus, if the generator 15 is operating, there will be produced in the output circuitof the detector D, a component having a frequency jceiving channels.

'to usethe channels C and C for receiving purposes at the same time thatthe transmitter T 15 operating to transnnt speech signals. \Vhen, however, the transmitter T is active, but is transmitting only un'modulatcd waves or wavesmodulated in accordance with telegraphic currents outside of the speech range, then all three of the receiving channels may be used,each to receive and detectan individual telephoneor other signal transmitted from the same or different stations. The telegraph side tone from the local transmitter will be small or negligible in its effect onthe telephone channelsf As noted, when the channels C and-C are to be used, the switch 13 is opened; when channels C and C are not in use, switch .13 may be either opened or closed but preferably closed. It should also be understood that the several. receiving instruments of channels C C and G, or any two of them, as the receivers 20 and 21, maybe brought to the earof a single listener or otherwise connected .to apparatus or a lineso that a single listener can hear themessages incoming on all channels so connected. Each station from which the messages are received can receive messages sent out from the station illustrated or from the other stations by providing asuitable number ofselective rc- In this. manner sevn radio stations can. communicate after the fashion of a several party conversation on a party telephone line. v

.Various adaptations to meet speeial circumstances can be made in the system as illustrated. Thus, additirinal stages of amplification may be added wherevernecessary, or some of the amplifiers illustrated may be omitted... Additional selective circuits, or selective circuits other than band filters may be utilized. The generator 12 may be omitted, In, this case, the modulated waves of 210,000, 220,000 and 230,000 cyclespassed by the band filter BF would eachbe selected by' a suitable selective circuit which would discriminate against the other frequencies. After selection, each carrierwave would be detectedby a detector similar to the detector D to reproduce the signal carried thereby. However, by making use of the generator12 in the manner illustrated, additional selectivity is obtained. The invention 1 is not fill limited tothe frequencies herein specified. Other frequencies may be selected as will be obvious to those skilled in the art. Furthermore,.it is not essential that all of the band filters illustrated pass the exact range of frequencies indicated. Thus, for example, the filters'BF BF iand BF might be modified in a mannerwell understood to exclude either the upper or lower side band of the particular modulated wave passing therethrough. If the combined frequencies, produced by conjointly detecting incoming and outgoing wa:ves,do not coincide with the range passedby the filter or selectiv circuit intendedto pass them, the desired coincidence may be obtained by readjusting either of the frequencies, or by readjusting the selective circuit or substituting another inits place.

As to systems of this type, it has been suggested that theyrwould be defective in that with large amplification in the receiving circuit and anunbalance of network BN with respect to th line TL the system would singror oscillate by the cyclic transfer'of energy from'the output circuit of amplifier LFA through the transmitter T, antenna: 4 and 9, and receiving. system B back to the point of beginning. By including the ether between the antennae as a conductive medium this forms a closed circuit. tests indicate that this kind of singing does not readily occur with large amplification and with considerable unbalance of the netis necessaryor convenient. Apparently the amusinging condition results from the fact that the'losses around the closed circuit are .atleast equal to the gains. These losses result III part fromthe fact that certain wave components are selected in the filters while others have their energy dissipated.

A feature of importance is the relative lo- 5 cation of the amplifier A and the band filter .BF. .mediate frequency or frequencies and then Instead of first selecting the interamplifying their energy it has been found .that increased selectivity results from placing the amplifier A in front of thecband :filter. The intermediate frequency and any accompanying disturbing waves are thereby ifirst amplified and then the intermediate frequency is selected. When the band filter LBF is placed afterithe amplifier A,.it has .0.

Experimental the distant station.

in any desired manner.

awmams certain apparent disadvantage of causing to 'not,'in.practical cases, be entirely eliminated,

the various waves which are impressed upon its input circuit will be combined to produce sum and difference frequencies. When the band filter follows the amplifier'all of these sum anddifi'erence frequencies will be suppressed except those Which lie within the transmissionband range of'the filter. This feature, among others described, is equally applicable in any system wherein beating oscillations are employedtoproduce an auxiliary carrier wave, whetherthe beating 0scillations are derived from the local transmitter or some other source.

Fig. 2 illustates a form of receiving antenna which may be employed. A receiving loop 9 is coupledto the detector D by an inductive connection to the circuit 11 or other suitable means. The loop 9' preferably includes an antiresonantcr loop circuit 10 tunedto the transmitter frequency to aid in keeping the energy ofthis frequency which is impressed on the receiver downto a value suitable to combine with that received from The circuit including theloop 9' is tuned tothe receivedfrequency and the loop 9' is preferably. directed at the distant station. 5

Fig. 3 illustrates anothermodified form of receiving antenna. In this instance, the antenna 9 is provided with a shunt path 22 to ground. This path 22 includes a loop circuit 23, tuned to the transmitted frequency f An additional circuit '24 serves to compensate for the reactance of thecircuit 23 at the frequency f, and to tune the antenna as a whole to thereceived frequency. The circuit 11 is coupled to the circuit 24 Any of the illustrated antenna systems or other modified forms may be used. For general purpose work that of Fig. 2 is to be'preferred.

Having described the invention in detail and certain forms of apparatus desirable for use in carrying it into effect, the features inherent therein which are believed to be novel will be described in the appended claims.

I claim 1. A signal transmission system comprising a station having means for transmitting high frequency waves. means for receiving high frequency waves, means forcombin ing the energy'of said waves-to produce an auxiliary frequency waveymeans for derivli e ing signaling frequency waves from said auxiliary waves, a line tcrnnnating at said station, mcansatsaid statlon for transmitting said derived waves over said line to a distant point, and means for causing the transnntted high frequency waves to be with waves of said varied carrier wave frequency, a telephone line, and conjugate connections from said line to the transn'iitting and receiving means,respectively.

3. A two-way signaling system com 'irising means at one station, includingan antenna, for producing and radiatinga carrier wave, means including another antenna for receiving wavesfsaid last mentioned means com prising means for combining waves received from waves from a distant antenna, and two frequency translating devices in tandem for translating the frequency of the combined waves.

4. A station comprising an antenna for receiving energy from a distant station, a transmitting antenna,a detector for combining energy received by said receiving antenna with energy transmitted by said station from said transmitting antenna, and a second detector for detecting the combined energy. a

5. Terminal apparatus for two-Way telephone communlcation comprising a radio transmitter including a transmitting antenna for transmitting on a given frequency, a radio receiver including an antenna tuned to a frequency differing from that of the transmitting wave, modulating apparatus for varying in accordance with speech, the transmitted waves, the receiving antenna being discriminatory against the transmitted waves in favor of the received waves, said receiver including means for combining the transmitted and received Wave energy to produce other waves, and means to derive telephone messages from the other Waves.

6. A two-way signaling system comprising a receiver having means for receiving signals from a distant station, means for trans- .mittingvoice modulated waves, means for first crnnbining said received waves with said transmitted waves to produce an auxiliary frequencywave, means for subsequently detecting said auxiliary wave to produce the received signal, additlonal means for modulating the transmitted waves in accordance with code signaling impulses, and means for receiving such impulses.

7. A two-way signaling system comprising said first mentioned antenna with means fortransmitting asignal modulated wave, means for receiving by first combining received Waves with energy of the transmitted wave frequency to produce an auxiliary carrier wave, means for subsequently detecting the auxiliary carrier wave to produce the desired signal in combinationwith means for modulating the transmittedwave in accordance with speech,'andmeans for ca using non-interfering signaling changes in said wave. r

S. A two-way signaling system compris ing incombinatio'n, means for transmitting a signal modulated wave, means for utilizing energy of the transmitted carrier wave frequency combining it with the energy of received waves to produce auxiliary carrier waves, means for detecting the auxiliary carrier waves to produce signals, and means for separating. and separately receiving telephonic and telegraphic messages incoming on the same carrier frequency of the received waves.

ing means for utilizing the energy of the transmitted wave by combining it with energy of received waves toproduce auxiliarycar ier Waves, means for detecting the aux- 9. A two-way signaling system'comprisiliary carrier-waves to reproduce signals, a

bandfilter for selecting'said auxiliary carrier wave, means for producing" from the selected wave a second auxiliary carrier wave, means for selecting said second carrier wave and means for deriving a signal therefrom.

. 10. In a two-way radio communication system, a pair of distantly located stations one of which comprises a transmitter and a receiver, a transmitting antenna for said" transmitter, a receiving antenna for said receiver, said transmitter including a source of radio frequency continuous oscillations, the difference between the operating frequency of said source and the frequency of waves incoming from the distant station be, ing a beat frequency above the usual fre quencies essential in speech waves, means at said receiver for detecting and indicating the signal components of said beat frequency,

and a tuned loop trap circuit in said receiving antenna for ofiering a high impedance to waves of the frequency produced by said source. i

11. A two-way signaling system comprising means for utilizing energy of the transmitted wave frequency including means for combining it with energy of the frequency of received waves to produce auxiliary car rier waves, a lurality of signaling channels connected to the output circuit of said combining means, and means for translating the frequency of received waves a plurality of times before detecting them to reproduce the signal. i

30 sulting froni the combinatiomand receiving 12. Terminal apparatus for two-way radio telephone i COIIIHIUIllCtltiOIL comprising a radio transmitter including a transmitting antenna, for radiating, wavesto carry messages to a distant station, modulating apparatus forwvaryiiig in accordance with, speech the transmitted waves, a; radio receiver comprising an antenna and means for, combining enorgy of: the tv ifi quency transmitted from said transmitterwith energy of the frequency of waves received from a distantstation to produce other waves, and means for deriving telephone messages from the other waves.

13, Terminal apparatus for a two-way radio communication system comprising a loop antenna for receiving energy from a distant station, a transmitting antenna for radiating energy to awdistant station and to said loop antenna, a detector forcombining,

waves received by said loop antenna from said transmitting stat on and from said distant 'station to produce heat frequency-waves, and a second detector for detecting the beat fr uenc 1 waves to re roduce si nals. q 3 g 14. The method of signaling which comprises combining at a,carr1er wave station incomingv and outgoing carrier waves: each modulated in accordance with signals-to produce a wave different in frequency from each of said waves, detecting: the Wave reimam the ineo riii'ig signal separated from the out-' going signal;

tivecircuit, an auxi m Station anda source of oscillationsthereat, said auxiliary station! beingsufliciently distant from said selective circuit sothat the selective devices cannot be adjusted, from the auxiliary station, and,

means to supply oscillations from. the-auxiliary station to said translating device to translate received oscillations into oscillations which. maybe transmitted through the selective circuit;

16; A station compiiisin an antenna for receiving waves from a istant station, a transmitting antenna, a detector for combining, waves received by said receiving. antenna with waves transmitted by said station, from said transmitting. antenna, a second detector for detecting the combined: waves, and an indicating, device for indicating the waves produced by: the last mentioned detection.

In witness whereof, I hereunto subscribe my name this 24th day of September A. 1).,

JOHN FISH FARBINGTON. 

